Issue 48, 2014

Bicontinuous hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite with enhanced fast sodium and lithium ions intercalation chemistry

Abstract

Mixed polyanion materials with a 3D framework for battery electrodes have been attracting significant attention recently in view of the requirements to further improve energy storage and power densities. Herein, we present a design of a hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite as sodium- and lithium-storage cathode materials. The hierarchical structure is composed of a 1D rectangular Na7V4(P2O7)4(PO4)/C nanorod, which is coated by in situ residual carbon and wrapped by a reduced graphene-oxide sheet. The open network of graphene and the surface carbon coating of the Na7V4(P2O7)4(PO4)/C nanorod provide bicontinuous electron and ion pathways, providing a three-dimensional conductive network for efficient electron and ion transfer. The flexible electrode built from the hierarchical composite free of binder or conductive additive exhibits improved electron conductivity and higher sodium/lithium ion migration coefficients than the pristine Na7V4(P2O7)4(PO4)/C nanorod. It approaches the initial reversible electrochemical capacities of 91.4 and 91.8 mA h g−1 with high discharge potentials over 3.8 V (vs. Na/Na+ or Li/Li+) and good cycling properties with capacity retentions of 95% and 83% after 200 cycles at a 1 C rate in sodium and lithium intercalation systems, respectively. Even at 10 C, it still delivers 87.4% (for sodium) and 78.2% (for lithium) of the capacity and high cycling stability. Taking into consideration the compatibilities of both sodium/lithium ions and their superior electrochemical characteristics, the bicontinuous hierarchical composite is considered to be a promising high-rate capability electrode material for advanced energy storage applications.

Graphical abstract: Bicontinuous hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite with enhanced fast sodium and lithium ions intercalation chemistry

Supplementary files

Article information

Article type
Paper
Submitted
30 Aug 2014
Accepted
22 Oct 2014
First published
22 Oct 2014

J. Mater. Chem. A, 2014,2, 20538-20544

Author version available

Bicontinuous hierarchical Na7V4(P2O7)4(PO4)/C nanorod–graphene composite with enhanced fast sodium and lithium ions intercalation chemistry

S. Zhang, C. Deng and Y. Meng, J. Mater. Chem. A, 2014, 2, 20538 DOI: 10.1039/C4TA04499A

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